As long as the base Pokémon is legal, the clones should be legal. And no, you can't give a nickname to an event Pokémon unless you catch it in-game
You can nickname an event pokemon if you RNG for the same Trainer ID and Name (well, you don't have to RNG for the name... you just enter it. :-P) From what I've heard, there is no need for the Secret ID to be the same.










